• 한국해양공학회지
• /
• 제2권1호
• /
• pp.46-58
• /
• 1988

The experimental investigations on the motion characteristics of a marine riser both in air and water were performed. The static deflections and natural frequencies of the riser in air including the effect of static offset, were obtained from the experiment. These results were compared with those of theoretical prediction by using a simple asymptotic formula. In order to investigate the nonlinear motion characteristics of the riser subject to nonlinear viscous drag and large displacement, the forced oscillation tests both in air and water were performed. In the forced oscillation tests in air, it was found that the transverse motion due to geometrical nonlinearity grows when the amplitude of in-line oscillation exceeds a certain critical value, say, order of 1-2 diameters. The planar motions of the riser in water due to vortex shedding and the geometrical nonlinearity were described. Some of these results were also compared with those of theoretical analysis, which uses a numerical perturbation technique based on the derived linear asymptotic solutions, and found to be generally in good agreement.

• 한국분무공학회지
• /
• 제27권3호
• /
• pp.126-133
• /
• 2022

The objective of this is to experimentally investigate the effect of mixed jet on the oxygen transfer characteristics with the primary nozzle area ratio of an annular nozzle ejector for the application of a microbial fuel cell. A direct visualization method with a high speed camera system was used to capture the horizontal mixed jet images, and a binarization technique was used to analyze the images. The clean water unsteady state technique was used for the oxygen transfer measurement. The air-water mixed jet discharging into a water tank behaved similar to a buoyancy or horizontal jet with the primary nozzle area ratio. It was found that an optimum primary nozzle area ratio was observed where the oxygen transfer performance reached its maximum value due to the decrease of air volume fraction and the increase of jet length and air bubble dispersion.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2006년도 하계학술발표대회 논문집
• /
• pp.621-626
• /
• 2006

Regenerative evaporative cooling is known as an environment-friendly and energy efficient cooling method. A regenerative evaporative cooler (REC) consisting of dry and wet channels is able to cool down the air stream below the inlet wet-bulb temperature. In the regenerative evaporative cooler, the cooling effect is achieved by redirecting a portion of the air flown out of the dry channel into the wet channel and spraying water onto the redirected air. In this study, a horizontal regenerative cooler is considered. In the horizontal regenerative cooler, the flow direction of evaporating water has a right angle to the flow direction of supply air. This difference was investigated with visualization technique and simplified 2-module performance test was done in a thermo-environment chamber. Optimum design configuration is changed due to the wet channel which are easily fully covered with evaporating water and block the air flow inside the channel. Applying the optimized fin configuration design with the highly wetting surface treatment, a regenerative evaporative cooler was fabricated and tested to Identify the cooling performance improvement and operation characteristics. From the experimental results at the intake condition of $32^{\circ}C$ and 50% RH, the supply temperature was measured to be around $23.4^{\circ}C$. The cooling effectiveness based on the inlet dewpoint temperature was evaluated 73% which is almost close to the design expectation.

• 설비공학논문집
• /
• 제17권11호
• /
• pp.1005-1013
• /
• 2005

The use of river water as a heat source of a heat pump has the advantage in the performance compared to the use of atmospheric air because the temperature variation of river water over the year is relatively small. In this study, the performance of the heat pump system using river water as a heat source was numerically investigated. A simulation model for the 2-stage compression heat pump system was developed with each component model composed of compressors, heat exchangers, a flash tank and electronic expansion devices. The peformance of the heat pump system using river water was improved by $50\%$ compared to that using atmospheric air in winter conditions.

• 설비공학논문집
• /
• 제10권4호
• /
• pp.456-465
• /
• 1998

Effect of a non-absorbable gas on the absorption process in a vertical tube absorber was investigated numerically. The water vapor mined with air as the non-absorbable gas is absorbed into LiBr/water solution film. The flow is assumed to be laminar and fully developed in both liquid and gas phases. The diffusion and energy equations were solved in both phases to give the temperature and concentrations, from which heat and mass fluxes were determined. It was shown that the local absorption rate decreases as the mass fraction of air in water vapor increases. The vapor pressure of water at the liquid-vapor interface reduces significantly since the non-absorbable gas is accumulated near the interface. The effect of non-absorbable gases on absorption rate becomes larger as the mass flow rate of the vapor decreases. For small amount of non-absorbable gases the total absorption rate of water vapor increases as the mass flow rate of the vapor decreases. Total absorption rate increases as the mass flow rate of the vapor increases for large concentration of non-absorbables at the inlet of an absorber.

• 대한설비공학회지:설비저널
• /
• 제15권4호
• /
• pp.362-371
• /
• 1986

In the normal Refrigeration process, the condensation heat of refrigerant s not been used because of its low-temperature waste heat. To recover the condensation waste heat of R-12 refrigerator, a drying and hot water system was designed and experimented. The results obtained were summarized as follows: 1. As the temperature a temosphere was increased, the temperature of discharge gas of compressor was increased. And the temperature was $80-84^{\circ}C$ for air condensing type and was $68-71^{\circ}C$ for water condensing type during summer. 2. The condensation waste heat could be obtained up to $50-55^{\circ}C$ of drying heat-source and Hot water in summer. In this case, recovered rate was about $73\%$. And the more temperature of drying Heat-source and Hot water were increased, the more a recovered rate were decreased. 3. When comparing drying characteristics of Agro-products in dryer of waste heat utilization and Hot air, there was no quality difference in products. But drying time of the former was 3 Hours longer than the latter. 4. The condensation waste heat of compressor could be applied into the drying of marine products, the predrying of agro-products and making hot water. And showed high possibility of the waste heat using in low-temperature storage.

• 한국분무공학회지
• /
• 제18권1호
• /
• pp.9-15
• /
• 2013

Wall thinning of pipeline in power plants occurs mainly by flow acceleration corrosion (FAC), cavitation erosion (C/E), liquid droplet impingement erosion (LDIE). Wall thinning by FAC and C/E has been well investigated; however, LDIE in plant industries has rarely been studied due to the experimental difficulty of setting up a long injection of highly-pressurized air. In this study, we designed a long-term experimental system for LDIE and investigate the behavior of LDIE for three kinds of materials (A106B, SS400, A6061). The main control parameter was the air-water ratio (${\alpha}$), which was defined as the volumetric ratio of water to air (0.79, 1.00, 1.72). In order to clearly understand LDIE, the spraying velocity (${\nu}$) of liquid droplets was controled larger then 160 m/s and the experiments were performed for 15 days. Therefore, this research focuses relation between erosion rate and air-water ratio on the various pipe-flow materials. NPP(nuclear power plant)'s LDIE prediction theory and management technique were drawn from the obtained data.

• 대한방사선기술학회지:방사선기술과학
• /
• 제44권6호
• /
• pp.663-669
• /
• 2021

The purpose of this study was to evaluate the usefulness of the rice bolus for upper-lower extremity radiation therapy by Tomotherapy. The computed tomography images were obtained for air, water, and rice bolus. The average and standard deviation of the Hounsfield unit (HU) were measured for image evaluation. The conformity index (CI) and homogeneity index (HI) were calculated for dose distribution of the planning target volume (PTV) which was treated by direct mode with gantry angle (90 and 270 angle). The point dose of a total of ten axial planes was measured to confirm the different regions. The mean of HU was -999.72 ± 0.72 at the air. The water and rice bolus were -0.13 ± 1.65 and -170 ± 27.2, respectively. The CI (HI) of PTV was 0.96 (1.36) at the air. 0.95 (1.04) at the water bolus, and 0.95 (1.04) at the rice bolus. The maximum dose for air was 136 cGy which is about 32% higher than 103 cGy for water and 104 cGy for rice bolus. There was a statistical difference for point dose between air and water including rice bolus (p=0.04), however, no statistical difference between water and rice bolus (p=0.579).The rice bolus phantom for extremities radiation therapy could be not only the optimized dose distribution but also the convenience and equipment safety at Tomotherapy. However, additional research will be necessary to more accurately verify the clinical usefulness of rice bolus phantom due to not enough examination.

• 한국수산과학회지
• /
• 제5권2호
• /
• pp.50-56
• /
• 1972

기포막을 이용한 어구 어법을 고안할 목적으로 각종 기포막으로 해산어의 반응을 관찰한 결과는 다음과 같다. 1. 기포막으로 어군의 진로 차단 및 구집이 가능했다. 2. 송기 압력 $0.160kg/cm^2$일 때, 기포 발생용 파이프 내압이 $0.087kg/cm^2$ 이상일 때는 기포막이 순조롭게 형성되었고, 송기 압력 $0.087kg/cm^2$일 때, 그 내압이 $0.018kg/cm^2$ 이하이면 침수되었다. 3. 효율적인 기포막을 형성하기 위해서는 수심 80cm, 송기 압력 $0.160kg/cm^2$에서는 구멍 크기 $\phi$ 0.3mm 간격 30cm가 가장 효과적이었다(Table 2).

• 한국한의학연구원논문집
• /
• 제11권2호
• /
• pp.23-33
• /
• 2005

Four Properties and five Flavors of Drugs is interpreted by adaptation of human body to the environmental theory(天人相應). The Structural model of the body is compared with sky, earth, sun and moon (天, 地, 日, 月). The natural changes of the four seasons give rise to that of Four Properties and five Flavors of Drugs. On equal terms it is happened in our body. On this study we can draw an analogy between sky, earth, sun & moon (天, 地, 日, 月) and the body. The six bu(六腑) is related to the earth, the five ju(五主) to the sky, the five jang(五臟) to the sun, the meridians system (經絡) to the moon. When spring, the air is warm, the water element of the earth is ascending, and the earth gives birth to the sour flavor. Like this, the water element is absorbed by six bu and then is ascended to the meridian system. When summer, the air is hot and the water element of the earth is floated, the earth make the bitter flavor. In the same way, the six bu absorbed the hot air from the five ju and the water element is quickly absorbed by six bu and then the water element is ascended to the meridian system. When rainy season (長夏), the earth creates the sweet flavor The sweet flavor give warmer energy to the five jang and the six bu. When autumn, the earth change the sweet flavor into pungent. The earth gives warmer energy to the sky, because of cool weather According to same process, the pungent flavor give warmer energy to the five jang and the six bu, and the meridian system gets back the water element from the five ju. When winter, the air is cold and the water element of the earth is hidden. The sky and the earth are not interchangeable. At that time, the earth produce the salty flavor and the water element is keeping in the meridian system.